Apparatus and method for centering substrates on a chuck

Abstract

An apparatus and method for centering substrates determining on a chuck. The apparatus includes a chuck in a process chamber, the chuck configured to removeably hold a substrate for processing; an array of two or more ultrasonic sensors arranged in the process chamber, each ultrasonic sensor arranged relative to the chuck so as to send a respective ultrasonic sound wave to a respective preselected region of the substrate and receive a respective return ultrasonic sound wave from the preselected region of the substrate; and a controller connected to each ultrasonic sensor and configured to compare a measured position of the substrate on the chuck to a specified placement of the substrate on the chuck based on a measured elapsed time between sending the ultrasonic sound wave and receiving the return ultrasonic sound wave from each ultrasonic sensor.

What is claimed is: 
     
       1. An apparatus, comprising:
 a chuck in a process chamber, said chuck configured to removeably hold a substrate for processing; 
 an array of three or more ultrasonic sensors in said process chamber, each sensor of said three or more ultrasonic sensors configured to emit and detect ultrasonic sound waves, each ultrasonic sensor of said three or more ultrasonic sensors equally spaced from each other and arranged about a center of said chuck and positioned relative to said chuck so as to send a respective ultrasonic sound wave to a respective preselected peripheral region of said substrate and receive a respective return ultrasonic sound wave from said preselected peripheral region of said substrate; 
 a ceramic ring surrounding the chuck, wherein each ultrasonic sensor of the three or more ultrasonic sensors is notched into the ceramic ring, wherein a top surface of each ultrasonic sensor of the three or more ultrasonic sensors is coplanar with a top surface of the substrate, wherein a bottom surface of each ultrasonic sensor of the three or more ultrasonic sensors is coplanar with a bottom surface of the substrate, wherein a top surface of the ceramic ring is coplanar with a top surface of the chuck wherever on the ceramic ring there is a respective ultrasonic sensor of the three or more ultrasonic sensors, wherein the top surface of the ceramic ring is coplanar with the top surface of the substrate wherever on the ceramic ring there is no ultrasonic sensor of the three or more ultrasonic sensors, and wherein the bottom surface of the substrate is in direct physical contact with the top surface of the chuck; and 
 a controller connected to said array of three or more ultrasonic sensors and configured to compare a measured position of said substrate on said chuck to a specified placement of said substrate on said chuck based on a measured elapsed time between sending said ultrasonic sound wave and receiving said return ultrasonic sound wave for each ultrasonic sensor of said array of three or more ultrasonic sensors. 
 
     
     
       2. The apparatus of  claim 1 , wherein said substrate has a peripheral edge, and wherein each ultrasonic sensor of said three or more ultrasonic sensors is to detect a respective distance of said peripheral edge of said substrate from said ultrasonic sensor. 
     
     
       3. The apparatus of  claim 1 , wherein each ultrasonic sensor of said three or more ultrasonic sensors is positioned to detect a respective distance of a peripheral region of said top surface of said substrate from said ultrasonic sensor. 
     
     
       4. The apparatus of  claim 1 , wherein each ultrasonic sensor of said array of three or more ultrasonic sensors is attached to said ceramic ring and positioned to detect a respective distance of a peripheral edge of said substrate from said ultrasonic sensor. 
     
     
       5. The apparatus of  claim 1 , wherein each ultrasonic sensor of said three or more ultrasonic sensors is configured to operate in focused mode having a focal depth and a focal zone. 
     
     
       6. The apparatus of  claim 1 , wherein said controller includes a micro-processor and a memory unit. 
     
     
       7. The apparatus of  claim 1 , wherein said controller includes a micro-processor and a memory unit, said controller configured to compare said measured elapsed time between sending said ultrasonic sound wave and receiving said return ultrasonic sound wave for each ultrasonic sensor of said array of three or more ultrasonic sensors to a calibration time for said ultrasonic sensor. 
     
     
       8. The apparatus of  claim 7 , wherein processing of substrates is aborted if said measured elapsed time is different from said calibrated time by a specified amount of time for any ultrasonic sensor of said array of three or more ultrasonic sensors. 
     
     
       9. The apparatus of  claim 7 , wherein said measured elapsed time is recorded in said memory unit for each substrate processed. 
     
     
       10. The apparatus of  claim 1 , wherein said chuck is an electrostatic chuck and said chuck is configured to hold a semiconductor wafer having no machined or ground flats or notches formed on the edge of said semiconductor wafer. 
     
     
       11. The apparatus of  claim 1 , wherein there is an array of four of said ultrasonic sensors, each ultrasonic of said four ultrasonic sensors in said process chamber, each ultrasonic sensor of said four ultrasonic sensors equally spaced apart from each other and arranged about said center of said chuck. 
     
     
       12. The apparatus of  claim 1 , wherein said process chamber is a vacuum chamber and said apparatus is a plasma deposition or reactive ion etch apparatus. 
     
     
       13. A method, comprising:
 providing an apparatus comprising:
 a chuck in a process chamber, said chuck configured to removeably hold a substrate for processing; 
 an array of three or more ultrasonic sensors in said process chamber, each sensor of said three or more ultrasonic sensors configured to emit and detect ultrasonic sound waves, each ultrasonic sensor of said three or more ultrasonic sensors equally spaced from each other and arranged about a center of said chuck and positioned relative to said chuck so as to send a respective ultrasonic sound wave to a respective preselected peripheral region of said substrate and receive a respective return ultrasonic sound wave from said preselected peripheral region of said substrate; 
 a ceramic ring surrounding the chuck, wherein each ultrasonic sensor of the three or more ultrasonic sensors is notched into the ceramic ring, wherein a top surface of each ultrasonic sensor of the three or more ultrasonic sensors is coplanar with a top surface of the substrate, wherein a bottom surface of each ultrasonic sensor of the three or more ultrasonic sensors is coplanar with a bottom surface of the substrate, wherein a top surface of the ceramic ring is coplanar with a top surface of the chuck wherever on the ceramic ring there is a respective ultrasonic sensor of the three or more ultrasonic sensors, wherein the top surface of the ceramic ring is coplanar with the top surface of the substrate wherever on the ceramic ring there is no ultrasonic sensor of the three or more ultrasonic sensors, and wherein the bottom surface of the substrate is in direct physical contact with the top surface of the chuck; and 
 a controller connected to said array of three or more ultrasonic sensors and configured to compare a measured position of said substrate on said chuck to a specified placement of said substrate on said chuck based on a measured elapsed time between sending said ultrasonic sound wave and receiving said return ultrasonic sound wave for each ultrasonic sensor of said array of three or more ultrasonic sensors; and 
 
 placing said substrate on said substrate chuck; and 
 measuring a position of said substrate on said chuck using said array of three or more ultrasonic sensors and comparing said measured position to a specified position on said chuck. 
 
     
     
       14. The method of  claim 13 , wherein said substrate has a peripheral edge, and wherein each ultrasonic sensor of said three or more ultrasonic sensors is to detect a respective distance of said peripheral edge of said substrate from said ultrasonic sensor. 
     
     
       15. The method of  claim 13 , wherein each ultrasonic sensor of said three or more ultrasonic sensors is positioned to detect a respective distance of a peripheral region of said top surface of said substrate from said ultrasonic sensor. 
     
     
       16. The method of  claim 13 , wherein each ultrasonic sensor of said array of three or more ultrasonic sensors is attached to said ceramic ring and positioned to detect a respective distance of a peripheral edge of said substrate from said ultrasonic sensor. 
     
     
       17. The method of  claim 13 , wherein each ultrasonic sensor of said three or more ultrasonic sensors is configured to operate in focused mode having a focal depth and a focal zone. 
     
     
       18. The method of  claim 13 , wherein said controller includes a micro-processor and a memory unit. 
     
     
       19. The method of  claim 13 , wherein said controller includes a micro-processor and a memory unit, said controller configured to compare said measured elapsed time between sending said ultrasonic sound wave and receiving said return ultrasonic sound wave for each ultrasonic sensor of said array of three or more ultrasonic sensors to a calibration time for said ultrasonic sensor. 
     
     
       20. The method of  claim 19 , further including:
 aborting processing of substrates if said measured elapsed time is different from said calibrated time by a specified amount of time for any ultrasonic sensor of said array of three or more ultrasonic sensors. 
 
     
     
       21. The method of  claim 19 , further including:
 recording said measured elapsed time in said memory unit for each substrate processed. 
 
     
     
       22. The method of  claim 13 , wherein said chuck is an electrostatic chuck and said chuck is configured to hold a semiconductor wafer having no machined or ground flats or notches formed on the edge of said semiconductor wafer. 
     
     
       23. The method of  claim 13 , wherein there is an array of four of said ultrasonic sensors, each ultrasonic of said four ultrasonic sensors in said process chamber, each ultrasonic sensor of said four ultrasonic sensors equally spaced apart from each other and arranged about said center of said chuck. 
     
     
       24. The method of  claim 13 , wherein said process chamber is a vacuum chamber and said apparatus is a plasma deposition or reactive ion etch apparatus.